Sample Characterization

The demand for higher-quality products and the increasingly specific requirements concerning these products' components call for more efficient solutions. CEMTEC's aim is to tailor all the steps of the process—from the start of production to intermediate and final products—to the client's needs. In order to do this, grindability, energy consumption, and the chemical characteristics of the raw material have to be determined.

All characteristics necessary for designing customized plants are determined at the laboratory and pilot plant. This data is a prerequisite for further calculations and design parameters.


Density

Raw material processing is always about treating mixtures of different components, so determining their density or bulk density is very important for the entire process design and calculation of material flow. It is used for scientific empirical modeling as well as for analytical calculations. Furthermore, the raw density of an unknown mineral composition can be used to characterize it to a certain degree.

At the in-house laboratory, CEMTEC can determine

  • raw density and
  • bulk density

of a loose or shaken material according to various industrial standards and specifications.

The different densities are determined with conventional test instruments and modern equipment such as

  • liquid pycnometers
  • standardized measuring vessels
  • helium pycnometers

Surface

Beside particle size analysis, the most important dispersion characteristic of a sample is its specific surface, which is often used for quality testing or quality comparison in production. It is an important parameter for the characterization of porous and powdery solids as well as a clear indicator for the newly created surface when determining the ideal comminution step. Hence, measuring the surface should be an indispensable part of any product analysis.

In the laboratory, the surface can be determined with:

  • the Blaine test
  • the BET method

The Blaine test is based on the principle of measuring the time a certain volume of air requires in order to flow through a previously defined sample. The specific surface can be calculated based on the density, device constants, a standardized reference sample, and air viscosity. With the instrument developed by CEMTEC, specific surfaces of several 100 to 50,000 Blaine (cm²/g) can be measured.

The BET method was named after its inventors Brunauer, Emmett, and Teller. The surface is determined based on the property of solids to adsorb gas molecules on their surface. If the adsorption isotherms of the gas (usually nitrogen) are known, it is possible to calculate the number of adsorbent gas molecules. By multiplying this number by the space required by the molecule (in the case of nitrogen: 16.2 × 10-20 m²), you can calculate the sample's surface.

Particle size analysis

Particle size analysis is necessary for extensively characterizing a product. The result of such an analysis is called particle size distribution, which is used for calculating various characteristic parameters. A product's particle size distribution has a significant effect on the material's properties. Depending on the respective particle size, CEMTEC uses various methods:

  • Manual screening and screening via screen tower or air jet screen
  • Sedimentation method
  • Laser diffraction

The particle size distribution obtained this way also depends on the measuring principle. Therefore, in order to ensure the best characterization possible, CEMTEC's experts work closely with the client and define the best analysis method for determining the particle size of the desired product.

In CEMTEC's laboratory, the entire particle size determination range mentioned above is covered. The following equipment is available:

  • Several hand screens
  • Vibrating screen, type Retsch
  • Air jet screen, type Hosokawa Alpine
  • Sedigraph II, type Micrometrics
  • Mastersizer 2000, type Malvern
  • Mastersizer 3000, type Malvern

Moisture Determination

Various methods such as the drying method, the Karl-Fischer-method, and the infrared absorption (surface moisture) can be used to determine moisture content. Beside the Karl-Fischer-method, the drying method is primarily used for determining the moisture of bulk materials in laboratories. CEMTEC also uses this highly accurate, gravimetric method of drying in its laboratory. In many cases, the moisture content of the material to be processed is, beside product fineness, decisive for selecting the ideal grinding plant as well as designing various material handling components, such as chutes and hoppers.

The moisture content of the supplied samples is determined with the following instruments, using the method described above:

  • Drying cabinet tmax = 300 °C for sample quantity mmax = approx. 50 kg
  • AND MX 50 Moisture Analyzer for powdery, non-flammable materials tmax = 200 °C, mmax = 10 g

Alternatively, you may determine the mass fraction of volatile components or the ignition loss in the kiln at a maximum temperature of 1,300°C to establish the moisture content.